In the Enhanced Registries grant (R01 HS20024), we proposed to enhance ImproveCareNow's (ICN) existing pediatric inflammatory bowel disease (IBD) registry by capturing data directly from the EHR and repurposing those data to support improvements in chronic care and comparative effectiveness (CE) research. We achieved these goals and transformed ICN from a clinical improvement collaborative to an operational Learning Health System (LHS) prototype. Key milestones achieved include transitioning all ICN Care Centers to an i2b2 (open-source) registry, obtaining data-use agreements and patient consent for the entire Network, improving data quality, implementing informatics tools to automate chronic care management, and conducting novel CE research. We collaborated with leading EHR vendors to create pediatric IBD-specific form templates that store data in discrete, interoperable formats. Some Care Centers have begun transferring EHR data to the registry, and implementation of distributed, local i2b2 systems is partially complete in a sub-network of children's hospitals. Thus, we designed and validated components of the digital infrastructure, strengthened processes to engage stakeholders, and improved patient outcomes. Despite our significant progress, there are still opportunities to strengthen the sustainability of the LHS. Th tools and procedures for transferring EHR data from Care Centers to the registry are fully architected and tested, but not fully deployed; there are opportunities to incorporate new sources of clinical data; and there is a need to better engage all LHS stakeholders. These are critical gaps; if are not closed, the sustainability of the registry and its usefulness to all stakeholders will not be assured. Our objective is to complete the transition of the IBD network to the EHR-enabled registry, link additional data sources to the registry, and engage stakeholders in helping to ensure the registry is developed to answer research questions that are meaningful to them. We have the following specific aims: (Aim 1): Enhance the existing digital infrastructure by 1) extending EHR data transfer to at least 75% of patients in the network, which represents approximately 20% of all children with IBD in the US, and 2) adding laboratory and medication data to the EHR- enabled data transfer. (Aim 2): Engage LHS stakeholders in a CE research prioritization process and ensure that the enhanced registry can support their top priorities. Continuing our work will make it more likely that we can bring the network to full scale, further increase the number of children with IBD in remission and extend the effort to additional chronic diseases.